Download ppt - Best Practices Phase Review Template

© 2006 Avaya Inc. All rights reserved.

Peer-to-Peer SIP TelephonyChristian Stegh,

N. America Practice Leader,

Emerging Technology and IP Telephony

Peer-to-Peer SIP TelephonyChristian Stegh,

N. America Practice Leader,

Emerging Technology and IP Telephony

VoIP Roundtable

2/14/2007

[email protected]

312-634-2404 one #

mailto:[email protected]

2© 2006 Avaya Inc. All rights reserved.

Agenda

Why P2PSIP is hot

Tutorial of basic concepts

Review of open issues

Introducing one-X Quick Edition

DRAFT UNTIL LAUNCH


Household P2P Names

Napster

BitTorrent

Kazza

Skype

Each is an island unto itself, using proprietary algorithms & signaling protocols.


Why P2PSIP?

No need for a centralized server– Phones self-organize into a telephony network and connect to

the outside via a simple IP/PSTN gateway or SIP trunk.

Cost savings:– No need for central equipment lowers capital expense

– The operating cost to install & maintain, and add users to the system is also low because no administration is necessary

– Inexpensive calling for consumers across the Internet

Redundancy in telephony architectures

Rapid turn-up time: After plugging the phone into a LAN and entering the user’s name into it, you’re ready to call.


No need for centralized server

Location information about the called party is kept within the endpoints themselves rather than in a server

Peers know about one another directly or by sharing information with other peers in the network

When a caller doesn’t know the exact location of the party it wants to call, it asks other network peers that are closer to the callee


P2PSIP

A suite of communication protocols that extend SIP to use peer-to-peer techniques for looking up and reaching users and resources.

vs.

Typical SIPP2PSIP


Redundancy in telephony architectures

P2P networks allow the work to be distributed evenly across peers

As peers leave — perhaps suddenly due to a crash — work is again redistributed

All nodes are working all the time and as such, standard telephony network infrastructure can become more robust by leveraging P2P

One node can backup another’s voicemail service


Standards Bodies Support is Swelling

IETF Birds of Feather groups started last year

Group’s size increases at each meeting

Numerous drafts have been submitted to the SIPPING (Session Initiation Protocol Project INvestiGation) workgroup

P2P SIP is not yet an official work item within the IETF, but there is a draft charter


Tutorial of basic concepts


Basics

P2P layer = distributed database

In Real Time Communications, data items stored are mostly information about a user

– Name

– IP address of phone

– Etc.

Requirements for a P2P layer for Real-Time Communication (RTC) are not the same as the requirements for file sharing


P2P Layer

The P2P layer is effectively a replacement for the registration, location, and lookup steps of a SIP server

It handles three things:

– How to register a phone or a user with the P2P overlay network (when the phone or user joins the network)

– How to lookup a phone or a user in the P2P overlay network (when a call to the phone or user is made

– How to dynamically shift information when peers join and leave, so that the load is balanced across peers and so the sudden loss of one or more peers doesn’t cause the network to lose track of its current registrants


Finding Peers

At the heart of the P2P algorithm is an efficient way to search for and retrieve information about the location of peers in the overlay network.

In small networks, all peers know each other

In large networks, too much memory would be required

– Distributed Hash Tables are the answer


Distributed Hash Tables

A DHT is a structured way of organizing the P2P network so that every peer only knows about some of the peers in the network.

More efficient than knowing about all peers,

A peer can quickly find out about another by asking other network users.

When a user tries to call a peer that is not in its table, it queries other peers, which quickly return the location to the user.


Popular DHTs include

Pastry

Tapestry

Chord - the basis for some early P2P SIP work

Since there are already many methods and more emerging, DHTs will likely take some time to standardize.


ChordUses a ring structure for the nodes in the overlay

Each node is assigned a unique ID and keeps a database of IDs of some of the nodes in the network

When a user searches for a node that is not in its own table, the node nearest to the destination address is contacted

The nearby node either returns the location of the callee or it sends the request to a node closer to the destination

Efficiently minimizes lookup table sizes


Routed queries like Chord

N4

Publisher

ClientN6

N9

N7

N8N3

N2

N1

Lookup(“title”)

Key=“title”Value=MP3 data…

Without more advanced algorithms, # of hops would be linear to # of peers


The Chord algorithm –Scalable node localization

Each node maintains

– Finger table

• Entry i in the finger table of n is the first node that succeeds or equals n + 2i

– Predecessor node

Search in finger table for the node that most immediatley precedes id

Invoke find_successor from that node

– Guarantees that a file is found in O(log(N)) steps


Standards Debate

DHT algorithms continue to be refined

But a bigger philosophical difference among early works needs resolution:

– Should the P2P protocol be integrated into SIP by adding new headers?

Or

– Should it be a separate and distinct layer?


P2PSIP vs. File-sharing

P2P layer for RTC P2P layer for File-sharing

# of data items # of nodes Can be >> # of nodes

Size of data items Small Can be large

Lookups Infrequent -- not a significant portion of a phone’s workload

Can be frequent

Join/Leave frequency Low (especially wireline)

Can be high


Enterprise vs. Consumer

See (at least) two distinct applications of P2P-SIP

Consumer telephony: Skype-like

Enterprise telephony: PBX systems for enterprises

These two applications have different requirements


Enterprise vs. Consumer

Enterprise Consumer

Hierarchy Natural groups (office, division, etc) that a P2P layer should respect.

Artificial?

Trust Model -- Authentication (“Can this phone/group join the network?”) is very important.-- Preventing rogue behavior not so important.

-- Authentication is not so important-- Preventing rogue behavior is important.

Scale 10,000 peers is a large network 10,000 peers is a small network


Merging non-P2P clients into the Model

SIPUAA

UAPeer

E

UAPeer

DProxyPeer

P

RedirPeer

R

PeerQ

GatewayPeer

G

UAPeer

F

NAT

NATUA

ClientC

P2PSIP Overlay with peers speaking Peer protocol

P2PSIPClient Protocol


Sample Message Flow

Client calling a Peer:1) Client C sends a query to Peer Q for the location of User U.2) Messages are exchanged between peers, and User U is

determined to reside on Peer F3) Peer Q sends response back to Client C.4) Client C sends SIP Invite message to Peer F.

UAPeer

E

UAPeer

DProxyPeer

P

RedirPeer

R

PeerQ

GatewayPeer

G

UAPeer

F

NAT

NATUA

ClientC

P2PSIP Overlay with peers speaking Peer protocol

P2PSIP Client Protocol

SIP Invite


Some Design Questions

Peer vs Client Protocol: Are these the same things, or not? Do we really need a Client protocol? Are either SIP?

How to find a media relay? Does it have to be network-path optimal?

How best to arrange NAT traversal?

Security: If peers are untrusted, how do we protect sensitive messages flowing through them?

Credentials. Certs from a CA? Self-signed?

Bootstrapping. How to start from zero?


Small Office Challenges

Very Small Business

Answer: Quick Edition 2.0

Very Small Business

No local tech support, limited technical knowledge

Need solutions that can easily grow with the business

Communications must be completely reliable and secure

Costly moves, adds and changes

More home and remote workers

Branches

No local tech support, limited technical knowledge

Managing branches is a real headache

–Different systems / vendors

–Ability to manage

–Communications must be completely reliable and secure

Costly moves, adds and changes

More home and remote workers


Avaya one-X™ Quick Edition Release 2.0 Intelligent Communications for the Smallest Office

IP Telephony for Small offices

– SIP-based peer-to-peer technology, no centralized hardware

– Voicemail, auto-attendant, call processing etc – all in the phone

Dramatically simple, cost effective, productive

– Default install in minutes, customize as required

Release 2.0 delivers– SIP Trunking, Multisite

Provisioning Tool, QOS, Call Park, Page and Retrieve, Teleworker


Avaya one-X Quick Edition Release 2.0 P2PSIP Attributes

Simple – Set up and make calls in minutes, customize as required

– Server-less configuration reduces acquisition costs, TCO

Cost effective– Reduce number of trunk lines

– Commonly used features built into the phone

– Centralized management reduces maintenance costs

Connected– Designed for Branches, or Very Small Business

– Enterprise wide dial plans drive efficiency

– Leverage internet infrastructure while maintaining voice quality

29© 2006 Avaya Inc. All rights reserved. 29© 2006 Avaya Inc. All rights reserved. Avaya Proprietary. Not For Distribution. Use pursuant to Company instructions.

Peer-to-peer discovery, setup

WAN

LAN

Standalone Configuration

Multisite Provisioning

Tool

Teleworker

HTTPS

P2P/SIP

Quick Edition Branch

SIP Service Provider

G10Gateways

PSTN


WAN

30© 2006 Avaya Inc. All rights reserved. Avaya Proprietary. Not For Distribution. Use pursuant to Company instructions.

PSTN

Peer-to-peer discovery, setup

WAN

LAN

Branch Configuration

Multisite Provisioning

Tool

ConvergedCommunication

Server,SIP Enablement

Services

CommunicationManager

SIP

Teleworker

HTTPS

SIP

P2P/SIP

G10

Gateways

HQ

Branch

Quick Edition Branch


Quick Edition Teleworker

WAN

InternetVPN

VPN

Teleworker

Teleworker

Ext 202

Ext 200Ext 201

Ext 204 Ext 203

Ext 202

Ext 201 Ext 200

Ext 203Ext 204

1. The Quick Edition teleworker feature provides Quick Edition functionality to remote workers of local Quick Edition sites

Teleworker over Internet (VPN)

Teleworker over WAN

2. Teleworker is a mode of operation in the 4610 and 4621 phones which allows Quick Edition to have presence as part the local site dial plan via a VPN or WAN connection

3. VPN connectivity over the Internet is provided by VPN routers which provide for secure LAN access to the branch

5. The VPN router is only required to route IP unicast traffic to/from the LAN and remote connection

4. Teleworker mode removes the dependency of IP multicast traffic which is required for operation on the local LAN

8. This same VPN router can be used to provide data connectivity for a PC to the local network if desirable

6. The teleworker phone can then be moved to/from the remote location and the local branch with the retention of all settings, voicemail, with backup while in transition

7. Standard call forwarding rules can also be applied to direct calls from an internal office phone for off-hours or virtual office day transparency


Features

PBX system for small-med organization

Is P2P; no central component.

– Phones cooperate to produce PBX functionality

Supports many standard PBX features:

– Call forward, call transfer, conference call, etc.

– Corporate directory (built automatically)

– Even features like voicemail, auto attendant, call logs, etc. are done in a distributed fashion.

– See www.nimcatnetworks.com for list of features


Features (cont.)

Designed for resiliency - system still works if some phones become unavailable.

Designed to be very “plug-and-play”

– For basic operation, the only configuration required is to enter your name on your phone.

Two ways to connect to outside world

– Through an optional PSTN gateway box (TTI)

– Though a SIP service provider


Implementation

Uses SIP for signaling

Uses a simple proprietary P2P layer

– Uses multicast to locate peers and join overlay

– Uses both multicast and unicast to distribute info about each phone

– Each phone has complete knowledge of other phones

Uses various proprietary schemes for distributing services in the P2P environment


More information

http://www.p2psip.org/

http://www.cs.rutgers.edu/~rmartin/teaching/fall04/cs552/lectures/p2p.ppt

http://www.mpi-inf.mpg.de/departments/d5/teaching/ws03_04/p2p-data/11-18-paper1.ppt

www.avaya.com/quickedition